linux-kernel - Re: [ckrm-tech] [PATCH 4/7] UBC: syscalls (user interface)

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Message-Id: <1156382435.8324.31.camel@galaxy.corp.google.com>
Date:	Wed, 23 Aug 2006 18:20:35 -0700
From:	Rohit Seth <rohitseth@...gle.com>
To:	Magnus Damm <magnus@...inux.co.jp>
Cc:	Rik van Riel <riel@...hat.com>, ckrm-tech@...ts.sourceforge.net,
	Dave Hansen <haveblue@...ibm.com>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrey Savochkin <saw@...ru>, devel@...nvz.org,
	hugh@...itas.com, Ingo Molnar <mingo@...e.hu>,
	Kirill Korotaev <dev@...ru>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Pavel Emelianov <xemul@...nvz.org>
Subject: Re: [ckrm-tech] [PATCH 4/7] UBC: syscalls (user interface)

On Tue, 2006-08-22 at 12:58 +0900, Magnus Damm wrote:
> On Mon, 2006-08-21 at 18:16 -0700, Rohit Seth wrote:
> > On Mon, 2006-08-21 at 11:47 +0900, Magnus Damm wrote:
> > > On Fri, 2006-08-18 at 07:45 -0700, Dave Hansen wrote:
> > > > On Fri, 2006-08-18 at 12:08 +0400, Andrey Savochkin wrote:
> > > > > 
> > > > > A) Have separate memory management for each container,
> > > > >    with separate buddy allocator, lru lists, page replacement mechanism.
> > > > >    That implies a considerable overhead, and the main challenge there
> > > > >    is sharing of pages between these separate memory managers.
> > > > 
> > > > Hold on here for just a sec...
> > > > 
> > > > It is quite possible to do memory management aimed at one container
> > > > while that container's memory still participates in the main VM.  
> > > > 
> > > > There is overhead here, as the LRU scanning mechanisms get less
> > > > efficient, but I'd rather pay a penalty at LRU scanning time than divide
> > > > up the VM, or coarsely start failing allocations.
> > > 
> > > This could of course be solved with one LRU per container, which is how
> > > the CKRM memory controller implemented things about a year ago.
> > 
> > Effectively Andrew's idea of faking up nodes is also giving per
> > container LRUs.
> 
> Yes, but the NUMA emulation approach is using fixed size containers
> where the size is selectable at the kernel command line, 
[Apologies for late reply..]

Yup, if we run with fake NUMA support for providing container
functionality then dynamic resizing will be important (and that is why I
made the initial comment of possibly using memory hot-plug)

> while the CKRM
> (and pzone) approach provides a more dynamic (and complex) solution.


...this complexity is not always a positive thing ;-)  (I do like core
of CKRM stuff FWIW).

-rohit

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